Author Topic: Rd400 crank rebuild different bearings  (Read 235 times)

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Offline rd400greenhorn

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Rd400 crank rebuild different bearings
« on: May 06, 2021, 11:41:44 AM »
Hi guys
So, had a crank rebuild, it came with smooth bearings, mening they did not have the pin on Them that sits in the engine cases.

Is this a problem?
Tips, recommend?

Offline rodneya

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Re: Rd400 crank rebuild different bearings
« Reply #1 on: May 06, 2021, 12:11:05 PM »
Are there grooves in them for am oring or completely smooth?
If they are completely smooth I would definitely not use that crank builder again. Some people will use green locktite to hold the bearings fro spinning, but in mu opinion the wrong bearings have been used.
Does the clutch side bearing  have a groove for the clip at least?

Offline rd400greenhorn

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Re: Rd400 crank rebuild different bearings
« Reply #2 on: May 06, 2021, 12:32:04 PM »
well yes sorry, let me correct.

the outer bearings have the groove for ring and seal on the other side, no problem. iam only talking about inner bearings, which stock has a pin going into small hole in the engine case before you seat the crank in the case.

those 2 bearings are now smooth, ergo they have no pins.

Offline bitzz

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Re: Rd400 crank rebuild different bearings
« Reply #3 on: May 06, 2021, 02:29:37 PM »
The outer bearings MUST have grooves. Those rings locate the crankshaft in the cases in the "X" axis

The idea of the "pins' is if you seize a bearing that pin will stop the bearing.
If you HARD seize a bearing, that pin plows a nice groove in your cases, ruining the cases.

I don't use "pinned" bearings. I think if you have seized crank bearings, cutting a groove in the case is just adding insult to injury.

There is no use putting any "glue" on the outside of the bearing.
If the bearing fits, anything you put on the outside of the bearing will get be displaced... getting GOO in your bearing. No thank you.
If the bearing DOESN'T fit, what are doing screwing around with goo. Your cases are done.

Offline Yamaha 179

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Re: Rd400 crank rebuild different bearings
« Reply #4 on: May 06, 2021, 02:46:01 PM »
A few years ago I asked Kevin Cameron about the rumor that you should use green locktite on the OD of the inner bearings you used that did not have anti-rotation pins installed.  He replied that he and Erv had tried that and upon disassembly found absolutely no indication that locktite had been used and therefore it was his opinion it was of no value.  The bearings used in the crank rebuild were Koyo 6206NRC3 obtained from a reputable dealer.  They were used because the OEM bearings were out of stock and on back order from Japan with an expected fill date of six months.  I always use OEM bearings and seals whenever possible, but I have used these bearings in the past and have never had any problem with them. 
Lyn Garland
PS:  Koyo bearings are made in Japan
« Last Edit: May 06, 2021, 02:56:23 PM by Yamaha 179 »

Offline gardenhosebusabottle

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Re: Rd400 crank rebuild different bearings
« Reply #5 on: May 06, 2021, 11:33:54 PM »
Hi guys,

I just looked up the Nachi Bearings I used on my old 400.  VXB online sells them (no locating bb for the case).  6206NRC3 are the inner bearings.  6305 NR C3 are the outer bearings, if my notes are correct (correct me if I am wrong!).  I found an old 2strokeworld.com post w/ Supertune saying that loctite 640 "is your friend".  i think they are like 15 bucks a piece now.

When RB was working full time.  He used silicone? o-rings to hold the bearings in place.  you have to cut the snap ring off for the 1/2 clip to fit. 

So loctite 640 or the right size o-ring.  I'd have to contact RB to find out what size the bearing o-ring is.  No problem running Nachi's multiple times.  Supertune himself recommended these bearings, so don't take my word for it, but they worked in my RD400F.

NOTE:  The price has increased on the bearings....the pic below is an old pic of an RB Designs crank rebuild for my 400F.



« Last Edit: May 06, 2021, 11:35:42 PM by gardenhosebusabottle »